Proposals have been made to improve the balance of the tans of tire tread rubber for reducing the fuel consumption of automobiles. More specifically, combinations of ingredients, separate mixing, and use of terminal modified rubber have been proposed.
For example, Japanese Unexamined Patent Publication (Kokai) No. 59-159839 describes a rubber composition obtained by wet mixing SBR and BR with different styrene contents, while Japanese Unexamined Patent Publication (Kokai) No. 2-129241 describes a process of production of a rubber composition comprising mixing a terminal modified/coupled rubber in a solution with carbon black, then mixing in a diene based rubber. On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 58-152031 discloses a master batch comprising SBR and BR, while Japanese Unexamined Patent Publication (Kokai) No. 57-00430 proposes separately mixing a high molecular weight rubber and low molecular weight rubber to produce a rubber composition.
Further, Japanese Examined Patent Publication (Kokoku) No. 5-1298 describes a rubber composition which improves the impact resilience and tensile strength of a vulcanite comprising a conjugated diene-based polymer having an aromatic tertiary amino group at a terminal portion of the conjugated diene-based polymer. On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 55-10434 describes, when producing a rubber composition for a tire tread by blending carbon black into a starting rubber comprising an amorphous 1,2-polybutadiene rubber and natural rubber and/or polyisoprene rubber (further possibly including a partially conjugated diene-based rubber), first mixing at least 25% by weight of the starting rubber component containing 1,2-polybutadiene and carbon black in a specific ratio, then adding and mixing in the remaining starting rubber to improve the fuel economy and safety of automobiles. Further, Japanese Unexamined Patent Publication (Kokai) No. 2-129241 proposes blending a terminal modified conjugated diene-based polymer with carbon black in an organic solvent to improve the tensile strength and abrasion resistance of the vulcanite.
Further, Japanese Unexamined Patent Publication (Kokai) No. 8-269243 discloses blending a high glass transition point SBR and a low glass transition point SBR master batch carbon black-containing.
However, the above separate mixing method of ingredients, use of terminal modified rubber, and other arts have problems, for example, the low effect in systems containing high amounts of oil and carbon black and improvements are still sought. Further, in the case of separate mixing, the concentration of the carbon black at the time of the initial mixing is increased and deterioration of the processability occurs such as scorching at the time of mixing. The amount of blending of the carbon black which can be separately mixed is also limited. Further, with use in generally used master batches, the desired effects are not obtained, therefore it becomes essential to modify the master batches.